The invention relates to a pulley having at least two discs which are provided on a pulley shaft and which are fixed against relative rotation, and wherein at least one of the discs is axially movable with respect to the shaft.
Such a pulley is known from European Patent Application No. 84200759.3 and is often used in a continuously variable transmission, wherein a driving belt is provided between a pair of pulleys. By means of frictional contact between the side faces of the driving belt on the one hand and the contact faces of the pulleys on the other hand, to which end the side faces of the driving belt are usually conical and the discs of the pulley enclose a V-shaped gap for accommodating the driving belt therein, power can be transferred from the one shaft to the other shaft. The transmission ratio of the continuously variable transmission can be varied by changing the effective gap width of the two pulleys, which width is adjustable by axial movement of the axially movable disc.
The known pulley works satisfactorily but nevertheless has a number of drawbacks. The known pulley is rigid in order to be able to take up the forces exerted on said pulley under all circumstances. This makes the pulley relatively costly, heavy and complicated, and besides its mass inertia is large, which is not conducive to the efficiency and the dynamic behaviour of the pulley in particular and of the continuously variable transmission in general.